This book discusses the study of simulating the growth of a thin film by chemical vapour deposition (CVD) processes. In recent years, due to the research in producing high-temperature films by depositing low pressures, the processes have increased and understanding the control mechanism of such processes has become very important. An underlying hierarchy of models for low-temperature and low-pressure plasma is presented in order to discuss the processes that can be used to implant or deposit thin layers of important materials. Due to the multi-scale problem of the flow and reaction processes, the authors propose multi-scale problems which are divided into near-field and far-field models.